This invention relates to an improved particulate products of combustion or smoke detector, and more particularly to detectors of the type employing solid state elements in an optical detector.
Two types of optical smoke detectors have usually been employed in the prior art to detect smoke. The first type is based on a measurement of the smoke obscuration of light emanating from a light source; and the second type employs the Tyndall effect and is based on a measurement of the light reflected by particles of smoke as the smoke passes through a beam of light emanating from a source of light.
A deficiency of many prior art detectors resided in the type of light sources employed. Non-solid state light sources, such as incandescent or neon lamps have a relatively short life, are brittle and sensitive to shocks. The lamp filament is brittle or the neon electrodes are very close to each other. Moreover, when an optical fire detector includes such a light source, the power supplied to the source is substantial. In a smoke detector installation having a large number of detectors continuously energized, the resulting power consumption becomes prohibitive in this era of higher electricity costs.
Incandescent light sources generally have a very wide spectrum of light emission, much of which is useless because the receiving photocell is responsive to only a small part of this spectrum.